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May 12, 2011 -- Ultraviolet light therapy and vitamin D creams are widely prescribed treatments for psoriasis, and now a new study may help explain why they work for so many patients.

Researchers say the vitamin D-based treatments increase the binding of a peptide called cathelicidin to DNA, which, in turn, inhibits the inflammatory response that triggers psoriasis.

The finding may one day lead to better treatments for the painful skin condition that specifically target cathelicidin, study researcher Jurgen Schauber, MD, of Ludwig-Maximillian University in Munich, Germany, tells WebMD.

“We were able to identify a novel, pro-inflammatory signaling pathway which helps us understand why [vitamin D-based] treatments work,” he says.

Treating Psoriasis

As many as 7.5 million Americans have psoriasis, a chronic, inflammatory disease that commonly causes thick, itchy, scaly patches on the skin.

While the causes are not completely understood, it is believed that the scaly patches occur when the immune system identifies healthy cells as dangerous ones and goes into overdrive, activating protein complexes called inflammasomes.

In the newly published study, Schauber and colleagues analyzed genes in skin biopsies from psoriasis patients and healthy volunteers.

They found that a gene encoding the newly discovered protein AIM2 was highly activated in the skin of the psoriasis patients, but not the samples from people without psoriasis.

Schauber explains that along with other proteins, AIM2 is a key player in activating an inflammation-triggering inflammasome.